Agassi played in far more diverse conditions- he had to beat serve-bots and net rushers on low bouncing grass, had to compete with dirtballers on clay and a variety of guys on the hard courts. One thing you could say about Agassi's Wimbledon was he was lucky to grab it just before Sampras went on a roll, same way Roddick managed to snatch his only GS title just before Federer went on his rampage.

35 year old Agassi competed with Fed for three sets in the 2005 USO final but yeah he sucks, innit.

Federer benefitted from a weaker clay era to get to the finals every year- once Guga, Costa, Coria, Gaudio, Corretja, Moya and the rest disappeared the competition got weaker and only Nadal could stop him. Still I was glad for him he got his career slam- as an all-court player he was the most suitable candidate of this era to get it.